Health Alerts

Action: The Snohomish Health District Health Officer Dr. Mark Beatty sends alerts via email to local health care providers. Alerts cover current local, regional or national health threats and important updates on medical care and protocols. Alerts are written as needed to cover urgent or emergent health issues.

Measles & vaccine preventable diseases training

Action requested: Be aware of current measles infection control recommendations and guidelines for assessing immunity for measles and vaccinating susceptibles.

Background

From January 1 to January 30, 2015, 102 people from 14 states (including Washington) were reported to have measles; most of these are believed to be due to exposure at Disneyland. This follows 644 cases reported from 27 states in 2014, the greatest number of cases since measles was eliminated in the U.S. in 2000 (only imported cases were documented). Most cases in the current outbreak either were not vaccinated or did not know if they had been vaccinated.

The current outbreak has raised community awareness. Local providers and public health agencies are receiving many calls about possible exposure or symptoms. Current guidance and resources follow.

Recommendations

In response to questions raised with public health:

Patients who call with symptoms of measles should not be allowed to sit in waiting rooms, but should be masked before entering a medical facility and evaluated in a negative pressure room. If such a room is not available, isolate the patient in an examination room that must not be used for two hours after the patient leaves.

Contact the Health District (425-339-5278) to report suspected measles and to obtain guidance for submitting specimens (preferably serum, nasopharyngeal swab, urine, & throat swab) to the State Laboratory.

The Washington State Department of Health has issued additional outbreak-specific guidance:

Prevention

All persons at risk for exposure and infection should be vaccinated or have other acceptable evidence of immunity as described below.

Infants aged 6-12 months may be vaccinated with MMR during an outbreak, ideally 1 month prior to any risk of exposure. Children who receive a dose of measles-containing vaccine before their first birthdays should be revaccinated with two doses of MMR vaccine, the first of which should be administered when the child is aged 12–15 months and the second at least 28 days later.

Adults, and Children aged 1 through 4 years who have received their 1st dose may receive the 2nd dose as long as 28 days have passed since the 1st dose during an outbreak.

Routine evidence of immunity:

Evidence of adequate vaccination for school-aged children, college students, and students in other postsecondary educational institutions who are at risk for exposure and infection during measles outbreaks consists of 2 doses of measles-containing vaccine separated by at least 28 days.

Laboratory evidence of immunity or lab evidence of disease

Born before 1957

Documentation of age-appropriate vaccination with a live measles virus-containing vaccine:

preschool-aged children and adults not at high risk: 1 dose

infants 6-11 months who travel internationally: 1 dose

school-aged children (grades K-12): 2 doses

health care workers: 2 doses

students at post-secondary educational institutions: 2 doses

adults with no other evidence of immunity who travel internationally: 2 doses

Assessing Evidence of Immunity

The criteria for routine evidence of immunity apply only to routine vaccinations. During outbreaks, recommended criteria for presumptive evidence of immunity might differ for some groups.

Vaccine doses with written documentation of the date of administration at age ≥12 months are the only doses considered to be valid. Self-reported doses and history of vaccination provided by a parent or other caregiver are not considered adequate evidence of immunity. Persons who do not have documentation of adequate vaccination or other acceptable evidence of immunity should be vaccinated.

Serologic screening for measles immunity before vaccination is not necessary and not recommended if a person has other acceptable evidence of immunity to these diseases. Similarly, post-vaccination serologic testing to verify an immune response is not recommended.

Documented age-appropriate vaccination supersedes the results of subsequent serologic testing. If a person who has 2 documented doses of measles- or mumps-containing vaccines is tested serologically and is determined to have negative or equivocal measles titer results, it is not recommended that the person receive an additional dose of MMR vaccine. Such persons should be considered to have presumptive evidence of immunity.

Persons who have measles-specific IgG antibody that is detectable by any commonly used serologic assay are considered to have adequate laboratory evidence of measles immunity. Persons with an equivocal serologic test result do not have adequate presumptive evidence of immunity and should be considered susceptible, unless they have other evidence of measles immunity or subsequent testing indicates measles immunity.

Outbreaks in Health-Care Facilities

During an outbreak of measles or mumps, health-care facilities should recommend 2 doses of MMR vaccine at the appropriate interval regardless of birth year for unvaccinated health-care personnel who lack laboratory evidence of measles immunity or laboratory confirmation of disease.

Health-care workers include all persons (medical or nonmedical, paid or volunteer, full- or part-time, student or nonstudent, with or without patient-care responsibilities) who work in facilities that provide health care to patients (i.e., inpatient and outpatient, private and public). Facilities that provide care exclusively for elderly patients who are at minimal risk for measles and complication of the disease are a possible exception.

If documentation of adequate evidence of immunity has not already been collected, it might be difficult to quickly obtain documentation of immunity for health-care personnel during an outbreak or when an exposure occurs. Therefore, health-care facilities might want to ensure that the measles immunity status of health-care personnel is routinely documented and can be easily accessed.

Background Information

The measles component of the combination vaccines that are currently distributed in the United States was licensed in 1968 and contains the live Enders-Edmonston (formerly called "Moraten") vaccine strain.

Measles-containing vaccines produce a subclinical or mild, non-communicable infection inducing both humoral and cellular immunity. Antibodies develop among approximately 96% of children vaccinated at age 12 months with a single dose of the Enders-Edmonston vaccine strain. Almost all persons who do not respond to the measles component of the first dose of MMR vaccine at age ≥12 months respond to the second dose.

Response to the vaccine is similar in almost all respects to that noted in natural infection. Antibodies first appear 12-15 days after vaccination and peak at 21-28 days. To assure protection, vaccine should be given one month (28 days) before any potential exposure to measles disease.

Measles Vaccine Effectiveness

One dose of measles-containing vaccine administered at age ≥12 months was approximately 94% effective in preventing measles (range: 39%–98%) in studies conducted in the WHO Region of the Americas. Measles outbreaks among populations that have received 2 doses of measles-containing vaccine are uncommon. The effectiveness of 2 doses of measles-containing vaccine was ≥99% in two studies conducted in the United States.

The Centers for Disease Control & Prevention is offering a two-day Epidemiology & Prevention of Vaccine-Preventable Diseases (The Pink Book) Course on September 16 ‒ 17, 2015. This is a comprehensive training on vaccination principles, vaccine-preventable diseases, and vaccines. Continuing education credits will be available. Attendees may also register for one of several free pre-course workshops on topics including HPV on September 15, 2015. For registration details and more information, visit: http://CDC2day.eventbrite.com